Any recommendations as to the best glue for sticking the battery holder used in the Woodstocks together? I've just acquired an HP25C where the battery holder sides have become detached from the solid part (ie that bit which forms the bottom of the actual calculator when the battery holder is in place) and remedial action is required.

Superglue works very well and you don't need a lot of it. Just apply a drop at about 1 cm intervals, and then immediately press the two parts together for about 30 seconds. Clean both contacting surfaces thoroughly first and remove any burrs or loose bits of plastic.